Influence of aluminum doping on the structural, optical, and photovoltaic characteristics of sol-gel-prepared MAPbI₂Br perovskite thin films

Employed sol-gel synthesis to fabricate undoped and (2, 4 wt.%) Al-doped MAPbI₂Br films for perovskite solar cells. X-ray diffraction (XRD) analysis confirmed the cubic structure of MAPbI₂Br. The 2 wt.% Al-doped film exhibited a larger crystallite size. UV–Vis spectroscopy revealed a small bandgap energy of 1.95 eV and a high refractive index at 2 wt.% Al doping. These films were integrated into perovskite solar cells. Electrochemical impedance spectroscopy (EIS) demonstrated a significant decrease in recombination rate with Al doping. Incorporating 2 wt.% aluminum (Al) doping into MAPbI₂Br led to a higher conduction band minimum (CBM) compared to pristine perovskite, suppressing interfacial recombination and increasing V_oc in solar cells. Our investigation highlighted that optimal 2 wt.% Al doping reduced carrier concentration while enhancing carrier mobility, thereby improving the charge collection efficiency of photoexcited electrons at the FTO electrode and increasing short-circuit current density (J_sc). The resulting 2 wt.% Al-doped MAPbI₂Br achieved maximum values of J_sc = 10.97 mA-cm⁻², fill factor (FF) = 0.773, V_oc = 1.09 V, and efficiency = 8.99%, showcasing its potential for low-cost perovskite technology. These findings offer valuable insights for identifying and developing new photovoltaic materials.